[roll third_party/pigweed] bazel: Use py_proto_library from rules_python

Some dependencies need to be updated to work with the latest
rules_python version.

Original-Fixes: b/266950138
Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/180537

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 5a3735537697d02..6a45a6e8af6a171
Roller-URL: https://ci.chromium.org/b/8763883189891221969
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Ic0bb2da31a72b48e9561ad4e6666f29fa348120b
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/181850
Commit-Queue: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Bot-Commit: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
diff --git a/third_party/pigweed b/third_party/pigweed
index 5a37355..6a45a6e 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 5a3735537697d02554d2dd7bf1177ccecf5dbbc6
+Subproject commit 6a45a6e8af6a1719d30633adeb21e1a4ad10ddc1